Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $182.32   11.352%   $203.017   $203.02   $203.00   $203.00  
  Purchase #2 $189.65   3.716%   $196.6974   $196.70   $196.70   $196.70  
  Purchase #3 $20.54   7.533%   $22.0873   $22.09   $22.10   $22.10  
  Purchase #4 $202.63   3.789%   $210.3077   $210.31   $210.30   $210.30  
  Purchase #5 $42.71   7.626%   $45.9671   $45.97   $45.95   $46.00  
  Purchase #6 $8.39   7.440%   $9.0142   $9.01   $9.00   $9.00  
  Purchase #7 $234.40   8.769%   $254.9545   $254.95   $254.95   $255.00  
  7 purchase totals = $880.64       $942.0452   $942.05   $942.00   $942.10